Evaluation of public relations efforts serves four purposes. First, evaluation provides practitioners a means of determining whether or not public relations efforts achieved objectives set prior to programming. Second, evaluation affords practitioners the opportunity to demonstrate the value of public relations to management, who may at times doubt the value of the efforts stemming from the PR department. Third, evaluation provides practitioners with information on which future efforts can be based by detailing what aspects of past programs were successful and, possibly more important, those that were not. Finally, evaluation of a program while it is in progress allows practitioners to steer efforts so that shortcoming can be addressed and unforeseen problems can be dealt with before they derail efforts completely.

Just as evaluation serves many purposes, it also takes many forms. Determining if objectives set before programming began were met is one means of evaluation. Gauging the impact of the effort quantitatively by investigating audience coverage, audience response, campaign impact, and environmental mediation is another. In either case, the evaluation provides data for practitioners to use to establish the worth of their efforts if the sources of measurement error are controlled.

In addition to the two forms of evaluation, two models of public relations research exist into which most measurement efforts can be categorized. Closed-system evaluation investigates only the messages and events that were actually planned for the campaign and how they affected intended publics. Open-system evaluation is more encompassing and looks at factors outside of the control of the public relations campaign. Both models provide a course of action that can be followed to effectively evaluate, in different manners, the results of programming efforts.

As an integral part of the public relations process that fundamentally has no beginning or end, evaluation serves as an important component of any program. Practitioners who wish to succeed in modern public relations must understand the purpose of evaluation, the forms of evaluation and the various models that categorize evaluative efforts. With a grasp of these concepts in hand in addition to an understanding of research, planning, and programming as presented earlier, practitioners are well armed to participate in the entire process of conducting quality and effective public relations.